The character 七 was originally a picture of a vertical line and a horizontal line bisecting each other, meaning something like, “cut and throw away the remainder”. 切 (OC *sn̥ʰiːds, *sn̥ʰiːd) represents the graphical meaning.

The top-most horizontal stroke is done from left to right. The vertical line and bottom-most horizontal line are done as one stroke, from top-left to bottom-right.